The long range goal of this project is to elucidate the physiological role of "Spot 14" (S14) protein. S14 is a nuclear protein that is abundant only in liver, lactating mammary gland and adipose tissue, and it is rapidly induced by dietary carbohydrate and T3. S14 has been directly linked to the control of hepatic lipogenesis in response to dietary carbohydrate and thyroid hormone (T3) by regulating specific lipogenic enzymes at the transcriptional level. The evidence was provided by experiments in which glucose and T3- induced S14 accumulation in cultured hepatocytes was blocked using an antisense oligonucleotide. Reduced lipogenesis in antisense-treated cells was explained by inhibition of the induction of several lipogenic enzymes (ATP-citrate lyase (ACL), fatty acid synthase (FAS), malic enzyme (ME), and pyruvate kinase (PK) as well as their mRNAs. This project will focus on the protein-protein interactions involved in this function of S14 and on the significance of S14 to metabolic regulation in the intact animal. Two independent approaches will be used to identify such interactions. The first is the yeast two-hybrid system. Recent studies have shown that S14 has a strong tendency for homodimerization, and we believe that this, in concert with the relatively high abundance of S14 cDNAs in the rat liver library that we have screened, has greatly reduced the chances of detecting other interactions.